Prefrontal cortex (RFC) is critical for a wide range of cognitive and social behaviors. Damage to RFC from neurological disease results in profound alterations in goal directed behavior. We will utilize a unique cohort of neurological and neurosurgical patients to examine several proposed RFC dependent behaviors. We will employ electrophysiological and behavioral approaches to determine the contribution of human prefrontal cortex to top-down control of visual processing, visual and auditory short-term memory and visual and auditory contextual processing. To achieve these three aims we will perform scalp electrophysiological studies in stroke patients with well characterized lesions restricted to lateral RFC. In separate experiments conducted under Specific Aim 4, we will record electrocorticographic (ECoG) signals from neurosurgical patients with chronic (4-7 day) subdural grid implants for localization of epilepsy. This will allow us to examine directly the cortical dynamics supporting some of the behaviors studied in Specific Aims1-3. Specific Aims 1-3 will address 1) Does RFC control visual search and face processing? 2) Does RFC control visual and auditory short term memory stores? and 3) What is the role of RFC in utilizing contextual information to guide decision making in the auditory and visual modalities? These three aims we will use the lesion-electrophysiology method to determine whether RFC is critical to support the behavior and will delineate the temporal dynamics of RFC control of posterior cortex engagement during these behaviors. Specific Aim 4 will examine whether ultra-high frequency gamma oscillations (60-200Hz) are generated in frontal and posterior cortices during attention, auditory memory and contextual processing. Further, we will examine whether theta frequency modulates high frequency gamma activity generated during cognitive processing. The research in Specific Aims 1-4 will employ event-related potential (ERR) recording and time frequency analysis extracted from either scalp EEC or ECoG data to achieve the proposed goals. The research program is built on previous work in our laboratory with an overarching goal to elucidate both the temporal dynamics and network properties of RFC contributions to cognitive processes frequently disordered in neurological disease. The work promises to provide novel insights into the neural mechanisms supporting normal and disordered cognition as well as providing information on patterns of neural re-organization subsequent to brain damage..